Improving Wettability and Interfacial Adhesion Between CF and PEEK by Sequential Plasma Treatments With Ar and Air

The fabrication of CF/PEEK composites using two‐dimensional braid premix has garnered significant attention as a promising alternative to traditional prepreg due to its flexibility and conformability. However, the microstructure and properties of the interface between CF and PEEK are crucial in determining the final mechanical properties of the composite and its potential applications. To enhance the interfacial wettability and adhesion of composites, a two‐dimensional braid CF/PEEK premix, consisting of CF as warp yarns and PEEK fibers as weft yarns, was subjected to plasma treatment using argon (Ar) and air in sequence for varying durations. Analytical methods, including SEM, AFM, Boehm titration, contact angle analysis, and microdroplet tests, were employed to compare surface roughness, surface acidic groups, surface energy, wettability, and interfacial properties. SEM and AFM analyses demonstrated that plasma treatment altered the fiber surface morphology and increased roughness with longer treatment times. Boehm titration indicated that the acidic groups on the fibers initially increased and then decreased in treatment duration. Surface energy calculations revealed specific alterations in components, with a notable enhancement in the polarity component. The work of adhesion ( W a ) between CF and PEEK, treated for different durations, exhibited an identically consistent change with the interfacial shear strength (IFSS). The IFSS improved from 44.87 ± 5.76 MPa to 61.73 ± 3.89 MPa following a 60‐s Ar and 60‐s air treatment, representing a 37.58% increase. This improvement underscores the effectiveness of plasma treatment, suggesting that modifying and controlling the fiber‐matrix interface offers a viable method for enhancing the interfacial properties of CF/PEEK composites.